Warning extended to 3pm

Our Winter Storm Warning has been extended to 3:00. So far the precip has tended to the heavy and frozen side, with many if not all locations reporting sleet, freezing rain or a mix. Accumulations are minor but meaningful, with many streets (even busy expressways) covered in a layer of ice/slush. Traffic is slow but volumes are light.

Thankfully the precip will trend toward all rain by late afternoon, with temps rising several degrees. But winds will pick up and that could result in power outages in places with ice accumulations.

Winter Storm Warning

NWS has just upgraded the whole area (except for far southern areas) to a Winter Storm Warning. This is a marginal storm but it may present some problems tomorrow morning.

Overnight toward dawn an area of snow and freezing rain will spread north. Snow totals will be light (1-3") in a few affected areas, but there could be an accumulation of ice. And is VERY tough to forecast freezing rain. A difference of just 1-2 degrees at the surface could lead to all snow, all freezing rain, or a mix. I think warm lake waters and ground in the city will lead to minimal snow and ice accumulations in the city and most of Cook County. But areas west and north could see meaningful ice as well as some snow. Pre up should switch to rain tomorrow morning into the afternoon, and by the evening commute things look better. Very high winds (40-50 mph) could lead to lakeshore flooding, isolated power outages, and flight delays.

Temps will be seasonal this week -- mostly 20s and 30s, sliding about 10 degrees into the first genuinely wintry air by New Year's Day.

Solstice + severe threat

In a truly unusual twist, we're talking about the winter solstice and the threat of severe thunderstorms at the same time. 

We celebrated (or not) the winter solstice last night at 10:48pm local time. We've already had the earliest sunset (Dec. 8th), and even though the sunrise times lag for a little bit (adding three more minutes until Jan. 10th), we'll start to add to each day's length from here. 

Tomorrow we're likely to have our 10th day of 50+ temps in Chicago this December, which is stunning (although the record is 16). Tomorrow could see see highs of 60+ in many locations, nearly 30 degrees above normal and threatening the record high for the day. 

Along with tomorrow's mild temps will come a flood of moisture -- dew points will be in the 50s, so it really will feel like March or April -- and a cold front behind the warm-up will threaten to spawn some strong or even severe thunderstorms. The primary threat is well to our south, and the mid-South could even see a tornado outbreak. Areas here or nearby could still see damaging winds in legitimately severe storms. In any case, high winds are likely along with the rain, so airport delays are possible.

Behind the storms skies will clear and temps will fall but remain ~10 degrees above normal. Both Christmas Eve and Christmas Day look partly to mostly sunny with highs in the low/mid 40s. 

There are no major cold-air outbreaks on the horizon for now. A few long-range models are trying to pick up some cold in the first week of January, but that's too far away to have much reliability. In general, there are no pending signs of a major pattern shift. 

snow for morning commute, then mild

A quick burst of snow looks likely late tonight and into the morning commute tomorrow. Accumulations should be fairly minor, but given the timing, during the height of the morning rush, even an inch of snow could have a significant impact on travel times. 

Beyond that, a very mild December pattern is shaping up. Temps are likely to break 50 later this week and into the weekend. No major intrusions of cold air are on the horizon and the month may actually get milder as we go. 

email/blog problems + storm recap + Thanksgiving + El Nino

Email updates and blog

I've heard from more than a few of you that these emails have gone missing, so I'm sending this twice. You should be getting it once from my email address and once from the blog ("Admin@....") if you've accepted the invitation to the Google Group. Since the emails got unwieldy I switched everything to the blog and the Google Group. You have to accept the invite from the Google Group to get the updates -- I'm not sending them from my email address anymore. (You can always go to the blog anytime if you think you've missed an email.) And please check your spam/junk folder because I imagine some of you are having that problem. If you still don't get them email me and I'll resend the invite from the Google Group. 

Storm recap

The Friday/Saturday storm was one for the record books (see below). Looking back at the forecasts, they were pretty good. Specifically, the core of Chicago got ~1" that melted quickly, right in line with the forecast. Many suburban areas got 4-6" so that also checks out. But things were definitely understated on the high side, as the high probabilities of >6" clearly did not point to the 8-16" that came down in some spots. It is hard to overstate how unusual that is -- especially in the third week of November -- but in any case, the forecast was clearly off in that regard. 

To highlight another aspect of this storm, downtown Chicago saw about an inch of snow while areas within the same county saw more than a foot. That is a massive dispersion even by Chicago standards. The heavy bands of snow targeting the N/NW suburbs were understated, but overall this was an impressively accurate forecast for such a complex, messy, and unusual storm.  

Officially, ORD recorded a storm total of 11.2" which is very impressive and #2 all-time for November (with the usual caveat about shifting record locations over the years). Chicago normally sees a storm with that much snow once every 3-4 years, and in November it is almost unprecedented. Other official tallies included 5.8" at Midway and 4.7" at NWS in Romeoville.

New records established, from NWS:

• A record maximum daily snowfall was set for November 20th for Chicago as 4.2 inches fell.  The previous record was 2.8 inches set in 1996.
  
• A record maximum daily snowfall was set for November 21st for Chicago as 7.0 inches fell.  The previous record was 3.0 inches set way back in 1893. (The 7" also makes it the third-snowiest calendar day ever recorded.)
  
• There had been zero flakes of snow recorded in Chicago before this major storm, and it goes down as the biggest-ever first snow of the season. 

• 
  

To give a little more perspective, the 11.2" just recorded at ORD is nearly one-third of the average for a full year of snow and it was higher than the average snow in any given month. Along those lines, and especially with December setting up mild at least from this distance, there is a chance that November will go down as the snowiest month of the 2015-16 winter. That has only happened once, in 1940. 

Thanksgiving

Temps today and tomorrow will stay in the 30s, although the sunshine will help melt some snow. Clouds will gather on Wednesday as temps warm into the 40s. Thursday looks wet with temps in the mid 50s. Details are tough at the point, but we could see quite a bit of rain, which would obviously create a lot of messy runoff. Email me if you have travel plans or need more specifics as the time approaches. The good news is that major travel delays look unlikely -- there are no large systems hitting any of the major airports on Wednesday/Thursday. 

El Nino

El Nino remains at record levels for now, and while mid-range forecasts are notoriously unreliable this is worth noting. The numbers are almost literally off the chart and in strong agreement regarding extreme December warming across much of North America, especially the northern tier of states. Nothing is written in stone, of course, but this is stunning:

Snow update

As of 12:30 snow totals are already toward the high end of the range from yesterday. And now a strong plume of lake-effect is sliding through the area. See the image below -- the darker green and yellow radar returns indicate near white-out conditions. Expect treacherous conditions for the next few hours in the affected areas. Snow should taper by mid/late afternoon.

Totals so far are near a foot far NW to 1-2" (since melted to bare ground) in the city along the lake. Officially:

@NWSChicago: Snowfall totals so far from the Airports as of Noon....
O'Hare... 7.1"
3 SW Midway... 3.5"
Rockford... 8.6"
Romeoville... 3.3"



KLOT - SuperRes Reflectivity Tilt 1 12:30 PM

snow update

A quick update as this storm comes together -- it's actually pretty impressive. 

No significant change to the outlook for the city and especially downtown. A couple of inches would be toward the high end. Warm pavement and the warming effect of the lake could keep precip more to the liquid side and/or limit accumulations. Rain will eventually shift to snow and it might look impressive at times, but it's not likely to pile up.

To the west, however, conditions look like to deteriorate more than previously expected. The center of the low continues to intensify and drive south. The axis of heaviest snow -- which has laid down more than a foot in Sioux Falls, SD and across portions of Iowa -- may now target northern Will County, DuPage, portions of Kane, and far W/NW Cook County. The same NEward gradient exists, as snow rates will fall as you travel to the SE (especially in areas within a few miles of the lake). Warm surface temps (near or just above 32F) also give me pause.  But there is growing confidence that very strong snowfall rates (well above 1" per hour) will overcome other factors. Many suburban areas could see 4-6" of snow. Some of the probabilistic models (see below) really like the odds for >6" in the darker oranger and reddish areas. 

No major change to timing. The rain will commence after sunset, with a transition to snow near midnight. The heaviest snow will fall between midnight and mid-morning, with the snow tapering after noon. 

Winter Storm Warning

Late yesterday the track of the storm did turn south, and last night we were upgraded to a Winter Storm Warning. There are a lot of caveats here, but the potential for sticking snow has increased dramatically. The Warning is in effect from 9pm tonight (Friday) through 3pm Saturday for the entire area north of I-80. (Thankfully the evening commute should have no effects.)

For starters, do not fall victim to the "OMG we're going to get a foot of snow" hysteria some people will undoubtedly start spewing. The 7-11" totals referenced in some forecasts, including from NWS, are both somewhat unlikely (in my opinion) and not applicable to the vast majority of people in the forecast area. 

What is clear is that there will be a sharp gradient from the NW to SE along which snow totals will decrease rapidly. Areas near DeKalb or even as close as Kane and McHenry counties have a decent shot at 6+ inches of snow. For the vast majority of the area's population it gets trickier and snow totals will almost certainly be well below that. 

Clouds will thicken this afternoon and precip will start as rain before potentially switching to snow tonight as we approach midnight. The best bet for now:

• 6+ inches of snow for far western and northern suburbs (Kane, McHenry, Lake)
• 3-6" for Dupage and far NW Cook, decreasing rapidly to the SE
• Trace to 2" for areas in Cook and Lake that are within 10 miles of Lake Michigan, including the entire city of Chicago. (I think for the core of the city-- within 2-3 miles of the lake -- there is a 30-40% chance that the snow never really piles up. It is hard to see much more than a couple of inches even if it does accumulate. )

For context, the difficulties with this type of storm are worth noting.

• An earlier or later shift from rain to snow -- a transition that is very hard to pinpoint -- can dramatically alter snowfall totals.
• The ground is still warm after a very mild fall. Even getting the atmospherics right might not be enough to get the snowfall totals right if the snow melts before accumulating. 
• The warm ground effect is amplified in the city. 
• The surface water of Lake Michigan is still near or above 50 degrees (10-12 degrees warmer than at this point last year), and winds initially blowing off the lake could well keep the precip in liquid form over much of the city. 

Miscellaneous:

• Should a 6" snow be recorded officially at ORD, it would be very rare -- it's only happened twice in Chicago (and four times in Rockford) since the late 19th century. 
• It has been 238 days since our last measurable snowfall in Chicago, which is slightly above average. 
• Temps will rebound into the 40s and 50s next week, so any snow won't last long. 
• No major storms are on the horizon here for holiday travel next week. 

snow possible

A storm lifting out of the Plains could impact the area beginning tomorrow (Friday) night through Saturday afternoon. A Winter Storm Watch has been posted for areas well west and north of Chicago, where 5-8" of snow could fall. I think far less than that is likely in and around Chicago, and I'll generally take the under on everything I've seen so far. A wind off the 50-degree lake water is likely to keep the precip as mostly or all rain in Cook County and south of I-80. Additionally, the ground is still warm which won't help accumulations. Western and northern suburbs could see a dusting to maybe 1-2" if things come together, with the switch to snow only happening on the backside of the storm Saturday morning/afternoon. A slight shift to the south or an unexpected intensification could change things, but for now the accumulations and impact look very modest for the city of Chicago, moderate at worst for most suburbs, but potentially substantial for areas well west and north (e.g., Rockford). I will only send an update if something changes and significant accumulations become likely for the Chicago area. 

And to pre-answer the question, this potential snow is behind schedule. The average date of first flakes is November 1st, and the average date of measurable snow is November 15th -- we've had zero snow so far this year. The season overall has been very mild, and beyond this cold over the weekend things look seasonal (although not as balmy as they have been). And for comparison, last year on this date the high temperature was 19, with a low of 9. 

Heavy rain possible

After a glorious day, clouds will fill in tomorrow (Monday) and rain will develop by Monday night or Tuesday morning. Some projections are pointing to 3" of rain, with more than that possible under some isolated thunderstorms. There is a chance that we'll need to back off those totals, but it's still a good idea to check gutters and downspouts for leaf blockages. Tuesday is likely to be a washout. By late week we'll be back toward more seasonal highs in the 40s.

In other news, enjoy these 50s and 60s -- a year ago right now we were going into one of the coldest ever weeks in November history with highs were in the 20s and low 30s. On Wednesday we have a good chance to crack 60; that date last year saw a high of 19.

Severe storms

We are under a severe thunderstorm watch until 11pm and a line of severe-warned storms is approaching rapidly from the west. Warnings may be issued for our area between 8:30 and 10:00, give or take. The main threat is winds gusting 60-70. These storms have a history of tornadoes and wind damage but they are weakening and not very impressive overall.

High winds 30-45 mph will continue on the back side of this massive system through tomorrow. Temps will fall into the 40s but the weekend should be nice with daytime temps in the 50s to near 60 and lots of sun.

Rain

Since a couple people have asked, please pardon this non-severe update regarding the Halloween rain.

The bad news is that light to moderate rain is very likely for the whole area through most of the day.

The good news is that it is likely to taper to light sprinkles or drizzle late afternoon toward sunset and it will end completely at some point after sunset (clearing from west to east). So, with patience most kids should get a shot at some trick-or-treating today.

The best news is that tomorrow through next week looks spectacular. Temps will warm into the 60s tomorrow and spend most of the first half of the week climbing into the low or mid 70s with lots of sun.

Hurricane Patricia

This has nothing to do with Chicago, so forgive me. But this situation is just astounding and potentially catastrophic.

Hurricane Patricia was a tropical storm wandering off the coast of Mexico just over 24 hours ago. Now it is the strongest hurricane ever recorded in the Atlantic or Eastern Pacific basins, and pretty much identical to the strongest hurricane ever recorded anywhere on the planet. Sustained winds are 200 mph with central pressure of 880 mb, and the storm is taking dead aim at the coast of Mexico. If NHC is right and it actually strengthens to a landfall wind speed of 205 it will be the strongest landfalling hurricane ever recorded. Beyond the EF5-tornado-level winds across a large area, there could well be a storm surge of 20+ feet. Given the short notice and poor communication, numerous bays and inlets, mountainous terrain inland...the potential exists for a horrendous human catastrophe. 

HURRICANE PATRICIA DISCUSSION NUMBER  14  NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202015  400 AM CDT FRI OCT 23 2015    Data from three center fixes by the Hurricane Hunters indicate  that the intensity, based on a blend of 700 mb-flight level and  SFMR-observed surface winds, is near 175 kt.  This makes Patricia  the strongest hurricane on record in the National Hurricane Center's  area of responsibility (AOR) which includes the Atlantic and the  eastern North Pacific basins.  The minimum central pressure  estimated from the aircraft data, 880 mb, is the lowest ever for  our AOR.  It seems incredible that even more strengthening could  occur before landfall later today, but recent microwave imagery  shows hints of a concentric eyewall developing.  If the trend  toward an eyewall replacement continues, it would cause the  intensity to at least level off later today.  The official forecast  shows only a little more strengthening before landfall.  Given the  very mountainous terrain that Patricia should encounter after  landfall, the cyclone should weaken even faster over land than  predicted by the normal inland decay rate.    Recent center fixes show that the hurricane is gradually turning  toward the right, and the initial motion estimate is 340/10 kt.  The  track forecast scenario remains about the same.  Patricia should  continue to move around the western periphery of a mid-level  anticyclone today and turn north-northeastward ahead of a trough to  the northwest tonight and Saturday.  The official track forecast is  somewhat slower than the latest model consensus and lies between  the GFS and ECMWF solutions.    The global models continue to depict the development of a cyclone  near the Texas coast over the weekend.  Based on the predicted  upper-level winds, this system should be non-tropical in nature.  However this cyclone is expected to draw significant amounts of  moisture from Patricia's remnants, and could result in locally  heavy rainfall over portions of the northwestern Gulf of Mexico  coastal area within the next few days.  Refer to statements from  local National Weather Service forecast offices for details.    We would like to acknowledge deeply the Air Force Hurricane Hunters  for their observations establishing Patricia as a record-breaking  hurricane.  Clearly, without their data, we would never have known  just how strong a tropical cyclone it was.    KEY MESSAGES:    1.  Confidence is high that Patricia will make landfall in the  hurricane warning area along the coast of Mexico as an extremely  dangerous category 5 hurricane this afternoon or evening.  Preparations to protect life and property in the hurricane warning  area should have been completed, or rushed to completion, as  tropical storm conditions are beginning to affect the area.  Residents in low-lying areas near the coast in the hurricane warning  area should evacuate immediately, since the storm surge could be  catastrophic near and to the east of where the center makes  landfall.    2.  In addition to the coastal impacts, very heavy rainfall is  likely to cause life-threatening flash floods and mud slides in the  Mexican states of Jalisco, Colima, Michoacan and Guerrero continuing  into Saturday.    FORECAST POSITIONS AND MAX WINDS    INIT  23/0900Z 17.0N 105.5W  175 KT 200 MPH   12H  23/1800Z 18.8N 105.4W  180 KT 205 MPH   24H  24/0600Z 21.7N 104.2W   60 KT  70 MPH...INLAND   36H  24/1800Z 24.5N 102.5W   20 KT  25 MPH...POST-TROP/REMNT LOW   48H  25/0600Z...DISSIPATED    $$  Forecaster Pasch

flash flood watch

The whole area is under a Flash Flood Watch until tomorrow morning. Rain is approaching from the SW, and the heaviest rain will arrive after sunset into the early AM. Another 1-2" of rain can't be ruled out, with higher amounts in certain locations. After some places -- particularly in the northern suburbs -- saw 3" or more of rain last night the ground is already saturated and the flooding risk is elevated. 

The good news is that the rain should clear out tomorrow morning. The temps should climb into the 60s with a drier north wind and some sunshine. Sunday looks really nice with sun and temps near 70.

In other news, I've had more questions about El Niño -- or El Grande Niño as this one is being called -- and the effects on our weather. The answer remains that El Niño looks like to persist if not strengthen into the winter, and that usually correlates with a mild winter in Chicago. But the correlation is not perfect, and this year's El Niño is being affected by "The Blob" -- a massive layer of warm water in the North Pacific. See below if you want to read more. 

So, we're still favored for a much wilder winter this year than the prior two just based on reversion to the mean -- those were two pretty harsh winters. And the building El Niño gives us a further likelihood of a mild winter. But it's too early to write that in stone, and The Blob may well throw a monkey wrench into the system. 

http://www.nws.noaa.gov/com/weatherreadynation/elnino_article.html#.Vfx5r99VhBf

http://ww2.kqed.org/science/2015/08/09/possible-spoiler-for-el-nino-a-battle-of-the-blobs/

https://en.wikipedia.org/wiki/The_Blob_(Pacific_Ocean)

season recap and outlook

Summer 2015 in Chicago closed slightly on the cool side -- roughly the 35th percentile for warmth. June was certainly cool and wet but the rest the summer was unremarkable. We had a significant run of consecutive highs >80 but fewer than average highs >90. There has also been an abundance of tornadoes in the NWS Chicago region -- 29 confirmed so far -- which sets the all-time record. 

And now that summer is technically over, the first week of September goes down as the warmest of the year based on average temperature. 

Looking ahead, there is a likely resurgence of warmth next week. After temps peak in the 60s Friday and through the weekend we're likely to get in back to the 80s next week. 

And looking ahead to winter, there is a very strong El Nino in progress. The implications are significant, but it's also easy to over-extrapolate. For example, the North Pacific is also very warm, which could cause a "blocking pattern" similar to the one experienced at times in the prior two winters. That's not likely, but it's possible. So yes, the prior winters with a strong El Nino 1982-83 and 1997-98 -- were mild in Chicago, but that's not something to write in stone just yet. The odds are definitely in our favor to have a milder winter than the prior one (and certainly milder than 2013-14) but exactly how this plays out is TBD -- seasonal forecasts made a few months in advance are not especially good just yet. 

https://climateillinois.wordpress.com/2015/08/31/temperature-departures-in-illinois-during-the-1982-83-and-1997-98-el-nino/

https://climateillinois.wordpress.com/2015/08/26/last-two-big-el-nino-events-milder-winters-in-illinois/

Tornado warning extended

Radar showing rotation right on top of Oak Brook mall. Moving NE into Elmhurst soon. Storm in whatever form will hit north side of city and northern burbs soon.

Blinding downpours and flash food warning for most areas.

Tornado warning DuPage

New tornado warning for Dupage. Downers Grove, Lombard, Elmhurst. Over Downers right now moving NE at 30-40.

Tornado warning -- Will County

New tornado warning for Will County. Radar indicated for now. Anyone in Joliet, New Lenox, Lockport and Lockport should be very aware and get in a secure building.

Tornado watch extended

The tornado watch has been extended for all areas, now including Cook and Lake counties. Still through 10pm. And either way a line of severe or near-severe storms is approaching from the SW -- now near Joliet and impacting areas NE through the next few hours. Most or all locations will feel the effects tonight. High winds, downpours and frequent lightning are likely.

tornado watch (partial coverage)

A tornado watch has been issued for western areas of the Chicago metro, including DuPage, Kane, Will, McHenry, and Grundy counties. This extends a previous watch that was further west of us, and it is in effect until 10pm.

Severe/tornadic storms are moving out of Iowa into western and central Illinois. These are not hte most impressive storms but they have the potential to continue developing for several hours. The main threat lies to our west, as indicated by the location of the watch area, but certainly the threat cannot be ruled out in the Chicago area. 

Thunderstorms -- severe/tornadic or otherwise -- may well come into the area this afternoon and through the overnight hours. 

As a sidenote, I hope everyone has dried out after the deluge last night. Parts of the northern and southern burbs got little if any rain, but a corridor along the Ike and through the city got blasted with 2-3+ inches of heavy rain with significant street flooding. It was a fairly compact little storm that got somewhat stuck over one area, and that's a really hard situation to deal with -- even NWS was very late in issuing a Flash Flood warning. So I apologize that there wasn't more notice but there is not a lot that can be done in advance of those situations.

Severe storm threat

We're in an area of "enhanced" threat for severe storms today (Sunday). Further north into Wisconsin there is a considerable tornado threat but here the main issue will be damaging winds. A bowing line of nasty storms could produce wind gusts of 60-80 mph if things come together -- possible but far from certain. Most likely timing is late afternoon into the evening and overnight.

Tornado watch

The entire area is under a tornado watch until 10pm. A severe thunderstorm watch was likely but conditions favorable for tornadoes escalated and SPC went that route. And right on cue a tornado-warned storm is near the Illinois-Wisconsin line at 2:30pm. Other non-severe storms are approaching from the west. Damaging winds, lightning and torrential downpours are possible anytime through tonight (although most hours will be dry). Slightly cooler tomorrow.

tornado watch until 11pm

All that sunshine during peak heating hours today has destabilized the atmosphere, and SPC has placed the entire area under a tornado watch until 11pm. The good news is that most of the Chicago metro area is on the fringe of the main threat area, but a tornado or another otherwise severe storm is still possible anywhere in the area. The prime time for storm development will be 5-6pm, and a couple of models are putting a supercell into the Chicago area around 7pm. We'll see -- the atmosphere is juiced but getting the development (let alone the exact timing and location) of severe storms right is difficult. 

Severe t'storm warning

The whole area is warned until 6:45 AM as a line of severe storms approaches from the NW. Winds above 60 mph are the main threat.

Storms, flash flood watch

The whole area is under a flash flood watch from pre-dawn tomorrow (Monday) through tomorrow night. An inch or two of rain could fall of storms develop as projected.

We are also under "Moderate" risk for severe storms. There is a building line of storms several hundred miles to our NW that could be in here around 4-8am tomorrow (Monday). A second round of storms is also possible in the afternoon. Neither scenario is assured but storms that do develop could easily become severe, with high winds the main threat.

More storms: "Enhanced" severe threat and Flash Flood Watch tonight

Bad news then good news, plus a recap of Monday night's storms.

Bad news:

• We are again under an "Enhanced" threat of severe storms tonight -- the whole area is outlooked, but south is more likely than north.
• The whole area is under a Flash Flood Watch starting tonight and running through Thursday morning.
• Several waves of heavy rain are likely to emerge from Iowa and traverse the area tonight. Some storms may pop this evening, but 12-6am is most likely for the heavy storms.
• Some spots might be missed but 1" looks like a good bet for most locations, with some getting 3-5" of rain if things come together. Lake County might get off easy, while Will County and points south are more favored for heavy rain.
• There is 2.0" of precipitable water in the lower atmosphere -- that is almost off the charts for this area. We're also sitting right on the edge of a huge dome of heat (triple-digit highs today on the Plains). Those two factors have often combined in the past with explosive results. 
• Some areas have already seen 7-8" of rain this month, and the whole area is running well ahead of normal for rain -- soils are saturated and the flood risk is higher than normal.
• After many locations saw ~4" of rain (expected roughly once per decade)  just 10 days ago on the 15th, a second such event would be truly unusual and potentially very problematic in flood prone areas.

Good news:

• Starting tomorrow, this exceptionally wet and stormy pattern looks like it will break down. From this distance, it looks like the Friday-Monday period should be sunny and dry with temps in the 70s and 80s.
• Tom Skilling is back from his umpteenth three-week vacation of the year.

Monday storms:

• The severe storms that came through far western and southern sections of the area on Monday night produced nine tornadoes. 
• One tornado near Coal City was rated a strong EF-3, with estimated winds near 160 mph -- the damage was impressive. There were seven injuries but none serious, and that seems miraculous given that this tornado occurred late at night and was obscured by a lot of rain.
  
• This is the strongest Chicago-area tornado since the Plainfield F5 of August 1990. (The monster EF-4 that hit Rochelle/Fairdale in April was not technically in the Chicago MSA). The Coal City tornado's path was 16.5 miles long and three-quarters of a mile wide at its peak. 
• Imagine this storm track about 30-40 miles (a rounding error) to the northeast...
• 
  
• 
  

Severe storms

There is a confirmed tornado on the ground west of Channahon and Joliet. This supercell is moving ESE and will affect Will and southern Kane counties. It might weaken as it approaches but redevelopment is also possible. A new tornado watch until 2:00 am is in place for Will and Kane (but not including Cook, Dupage or Lake).

Other big storms are popping elsewhere. One storm is just north of Carol Stream and is tracking east toward O'Hare. The atmosphere is primed and these storms show that the "cap" has been breached so more development is possible.

severe t'storm watch

We've just been put under a severe thunderstorm watch until 3pm. (And another one is possible for the evening hours after a break this afternoon.)

SPC almost went with a "PDS" -- Particularly Dangerous Situation -- watch, which is rare territory. They ultimately went against that, but the chance of severe weather is pegged at 80%, which is very high. 

A line of severe storms is approaching from the northwest right now. It will arrive in the far western suburbs between 10-11am and downtown between 11am and noon.

This line has a history of 80+ mph gusts and significant wind damage along with frequent lightning and brief heavy rains. 

A severe t'storm warning is likely with this line of storms. I won't sent an update unless something significant changes -- expect strong to severe storms across the area from ~10:30 through ~12:30. 

Severe threat Monday

We have two chances at severe storms on Monday. The first is a line that may develop late morning into early afternoon. The second looks less certain but is potentially more significant -- it would develop toward sunset. The set up has a lot of moisture and a lot of wind shear so things could get ugly. SPC has us under "enhanced" risk of severe storms and that is a fairly big deal. Definitely worth paying attention tomorrow.

tornado warning cancelled; flood threat increasing

The tornado warning has lapsed. (Note that reports of sirens outside the warned area were due to local officials jumping the gun.) In any case the threat has already passed, although isolated severe weather (wind, hail) remains possible. The ongoing threat of significant flooding is also increasing by the minute as wave after wave of drenching thunderstorms is orienting along an axis from west to east, right through the heart of the area. Everything in a corridor 30 miles to the north and south of downtown is under the gun right now, and significant downpours will continue for several more hours. Hardest-hit areas will see very high rainfall totals. Roadways, creeks/streams/rivers and low-lying areas are all at risk of flooding. Do not take any chances in crossing any water in a vehicle or on foot.

Traffic times are already very high, and both airports are being severely impacted. Train delays are likely as well. 

Tornado warning and flooding threat

Central Cook is under a tornado warning -- radar indicated a tornado near Maywood and Westchester moving east near/along the Eisenhower. This is unlikely to be a strong tornado but that will not prevent damage or injury. Take notice in the area and pay attention in areas to the east.

Most of the area is under a flash flood warning. After many places saw heavy rain earlier today, a new round of moderate to heavy rain is moving through. The earlier projections look light, if anything. Many places could see 2-4" of rain today, which comes on saturated soils.

The good news is that the rain should clear toward midnight and tomorrow looks dry and beautiful. But there will likely be significant water problems tonight for some spots.

flash flood watch

The entire area is under a flash flood watch until tomorrow morning. With all the recent rain the ground is already saturated, and today and tonight look likely to produce more heavy rain. 1-2" is a good bet across most of the area, with isolated 3-5" totals possible in spots that get stuck under a series of storms. Isolated severe weather is also possible. 

Severe t'storm watch, heavy rain

Severe t'storm watch for the area until 11pm. Several non-severe storms approaching from the west now. Big storms south near Joliet. All moving NE and most places will see storms tonight. Model estimated totals for the next 36 hrs are 1-3" across the area with local 4-5" totals possible.

Heavy rain

Starting tonight through tomorrow morning we're under the threat of heavy rain. An inch or more is a decent bet for almost the entire area (less north, more south) and certain spots could see a lot more than that. Areas along and south of I-80 are most favored, and given the deluge they've received recently the flooding threat is elevated there. Areas SW of Chicago are also under a tornado watch and isolated severe weather is possible throughout the area as well.

Weekend looks mixed. Saturday will be mostly dry (if cloudy) with just some light, passing showers. Sunday looks wet but won't be an all-day washout.

severe t-storm warning

A line of severe-warned thunderstorms is approaching from the west. Suburbs in Dupage are feeling the effects now, and if they hold together the storms will arrive along the lakefront before 5:00 pm. These are not terribly impressive storms, but CTG lightning, 60mph gusts, and small hail may occur along with brief heavy downpours. 

Heavy rain likely with threat of flooding, severe weather

Beginning late this afternoon and into tonight we'll enter a stormy period with at least a couple waves of heavy rain and embedded thunderstorms. 

The main risk is that some areas may see 2-3" of rain, with isolated spots even higher. It's been fairly dry but this rain could be enough to cause isolated flooding. 

Beyond tonight there will be periods of rain and storms for the next several days, although the majority of the hours will be dry and the weekend will not a be  total washout by any measure. Tomorrow looks mostly dry after morning showers clear out, but tstorm chances pick up again on Sunday.

Beginning Sunday night and going into Monday there is a better-organized threat for severe weather, as the multi-day severe outbreak in the Central Plains moves this way. Stay tuned on that. 

Temps will remain in the 60s and 70s during the day in most locations, although the usual lakefront spots may be cooler. Early next week a slight downturn looks likely for Tuesday/Wednesday ahead of a big warm surge that could put everyone well into the 80s again later next week. 

new severe t-storm warning

A new severe thunderstorm warning has been issued for a cell approaching the SW suburbs. 70-80 mph gusts and large hail have been reported. The storm is approaching Joliet and will be near Naperville shortly after 9:00pm. If intact it would move through the western suburbs and into Chicago between 9:30 and 10:00pm. It is a nasty storm right now and needs to be monitored -- it could intensify further or even produce a tornado.

Other storms remain severe but are moving out of the area. Far northern areas near the WI line are under a severe warning now but will be clear soon. The NW and N suburbs were especially hard hit. Damage west of the area near Rochelle is horrendous. There was a strong, long-track tornado on the ground for several dozen miles given early indications. The pictures and video are staggering.

The cold front is right behind this round of storms, so once this goes by we'll be in the clear. Areas should be into calm weather by 10:00pm far west and 11:00 to 11:30 near Lake Michigan. 

Tornado crossing I-90 bw Rockford and Chicago

A massive tornado is still on the ground. It just crossed I-90 and is heading into McHenry. Harvard and Woodstock and anywhere nearby need to shelter immediately. You won't see a clearer, stronger tornado in Illinois than this.

Massive tornado near far NW suburbs

A massive, deadly tornado just destroyed a small town SE of Rockford and is rapidly approaching the far NW suburbs. Dekalb going into mchenry County.

Another large PDS tornado west near Dixon.

PDD tornado near Rockford

This is very serious. Do not mess around if you happen to be near Rockford.

There are other tornado warned storms in the area as well but none in the immediate city or suburbs. More development to our SW threatens for the next 1-2 hours.


709 PM CDT...A CONFIRMED LARGE AND EXTREMELY DANGEROUS TORNADO
WAS LOCATED JUST WEST OF KIRKLAND...OR 11 MILES SOUTHEAST OF
ROCKFORD AIRPORT... MOVING NORTHEAST AT 45 MPH. A SECOND TORNADO
COULD FORM JUST EAST OF THE CURRENT TORNADO AND COME VERY CLOSE TO
THE TOWN OF KIRKLAND.

THIS IS A PARTICULARLY DANGEROUS SITUATION.

IMPACT...YOU ARE IN A LIFE THREATENING SITUATION. FLYING DEBRIS MAY
BE DEADLY TO THOSE CAUGHT WITHOUT SHELTER. MOBILE HOMES
WILL BE DESTROYED. CONSIDERABLE DAMAGE TO
HOMES...BUSINESSES AND VEHICLES IS LIKELY AND COMPLETE
DESTRUCTION IS POSSIBLE.

THE TORNADO WILL BE NEAR...
KIRKLAND AROUND 715 PM CDT.
KINGSTON AROUND 720 PM CDT.
GENOA AROUND 725 PM CDT.

OTHER LOCATIONS IMPACTED BY THIS TORNADIC THUNDERSTORM INCLUDE DAVIS
JUNCTION.

INCLUDING THE FOLLOWING INTERSTATE...
I-39 BETWEEN MILE MARKERS 104 AND 115.

Tornado warning for Rockford

A tornado-warned storm is moving into Rockford. Cells in this cluster recently produced a confirmed and large tornado near the Quad Cities.

Non-severe but significant thunderstorms are approaching Chicago's western suburbs right now.

More to follow as these storms develop and move rapidly to the northeast.

Tornado Watch today (4/9/15) to 11pm

NWS/SPC has just issued a Tornado Watch for our entire area until 11pm. The outlook calls for a "60% chance of 2+ tornadoes, 40% 1+ strong." 

More detail: "A FEW TORNADOES LIKELY WITH A COUPLE INTENSE TORNADOES POSSIBLE

     SCATTERED DAMAGING WINDS LIKELY WITH ISOLATED SIGNIFICANT GUSTS         TO 80 MPH POSSIBLE       SCATTERED LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 2.5         INCHES IN DIAMETER POSSIBLE

I thought they were on the fence about issuing any watches today, and about a half hour ago they issued a tornado watch for areas well west of us (past Rockford). But things are apparently coming together enough, in their opinion, to warrant a watch. This is a reasonable serious situation -- a similar tornado threat in Chicago might occur once or twice a year, if that. 

To update the overall outlook from yesterday, the entire Chicago area remains in the "Enhanced" risk area for sever storm development. That means that a severe storm is 30% likely to develop at some point today within 25 miles of any given point within the area. Again, the leaves a 70% chance that severe storms will not develop today. And of course the forecast could verify if a severe storm develops 25 miles away but does not impact your specific location. The same of course applies to the tornado watch. 

Any severe storms that do develop today are most likely from mid-afternoon through early evening -- call it 4pm to 9pm. We're likely to get at least two discrete rounds of potentially severe weather, so keep an eye open even after a storm has just passed. This also looks like a potentially low-coverage event -- a few discrete but powerful supercells may develop and hit hard in certain areas while other locations get nothing. Frequent lightning and heavy downpours are likely even if we avoid the severe threshold. And after several rounds of heavy rain this morning the ground is likely saturated in many places.

Between now and the development of any storms it will be cloudy with some peaks of sun and near 70 degrees in most spots. (It's only in the 40s well to our north due to the lake and the approaching cold front; the contract and plenty of available moisture is driving these storms.)

As mentioned yesterday, the mid-range outlook is quite warm and will likely feature above-normal rainfall. Temps tomorrow should climb to the mid/upper 50s in the afternoon with a lot of sun, and the weekend looks nice with more sun and 60s or even 70s by Sunday afternoon. More 60s and 70s with interspersed rain events looks likely for next week. 

resending -- new blog; severe weather possible, heavy rain likely

We've already had our first technical difficulties, so I'm resending this. Everyone should be added to the Google Group now and get this second post that way rather than directly from me. 

-----------------------------------

After many requests I've decided to join the 21st century -- or at least the first decade of the 21st century -- and post these weather updates and a few other resources on a blog. 

http://chicagosevereweather.blogspot.com/

I'm doing this now for two reasons. First, it's easier to create a Google Group than it is to maintain an email list and send the emails directly. Second, this will leave a permanent, easily accessible archive. After that "surprise" Monday-morning snow a few weeks ago -- I took the under on 1-2" of snow and we got 4-6" -- I heard about my shortcomings from more than a few of you. That's ironic because I didn't get any flack for the Super Bowl Snowstorm on February 1st, which I missed to a far greater degree. And I never hear about it when things go "right," so maybe I'm just doing this to amuse myself, but whatever. This blog will provide a platform for everything, whatever that's worth. 

You should have just received a welcome message from the Google Group. After this post you'll only get emails directly from the blog (via the Google Group) when there's a new post. You should get this message twice -- once from me directly and once from the Google Group.  Please email me if something isn't working. 

Now for the good stuff:

• After a very dry spring so far the pattern has turned wet. It is possible that we'll see as much rain (3-4") in the next 10 days as we've seen all year.
• Thunderstorms are likely late tonight. Some may produce downpours and hail.
• An outbreak of severe weather is possible tomorrow (Thursday) afternoon and evening. We're currently at an "Enhanced" level of risk for severe storms, which is the middle point of a five-point scale of risk. As always, the timing and specifics are difficult to pinpoint, but stay tuned. It's not going to rain all day, and it will be nice and warm (likely over 70 degrees) even down to the lakefront. But at this point any outdoor plans for Thursdayafternoon/evening look likely to be impacted, and there is decent potential for some really strong storms. 
• After this chilly weather things look likely to warm up. The 5-10 day models are all pointing to above-normal temps, so there is a good chance we'll see some warmth (60s and 70s in the afternoon) this weekend through next week, at least for those locations that escape Lake Michigan cooling. 
• In other news it is (or has been) snowing across parts of MN/WI and upper New England. So there's that.